1. What steel is stainless steel?
Stainless steel is a type of steel, steel
that contains carbon (C) was below 2% called the steel, is greater than 2%. The
addition of chromium in iron steel smelting process (Cr), nickel (Ni),
manganese (Mn), silicon (Si), titanium (Ti), molybdenum (Mo) and other alloying
elements improved the performance of the steel steel with corrosion (i.e. not
rust) that we often say that the stainless steel.
2, why there are different grades of stainless steel?
Stainless steel in the smelting process, due
to the addition of alloying elements in different varieties of different
varieties, adding different quantities. Its characteristics are different, in
order to distinguish between the different grades of crown, the following are
common decorative stainless steel "different alloy elements" content
is for reference only:
grade of steel (C) (Si) (Mn)
(P) (S) (Cr)
(Ni) (Mo) (Cu)
304 ≤0.08 ≤1.00 ≤2.00 ≤0.045 ≤0.03 18-20 8-10
301 ≤0.15 ≤1.00 ≤2.00 ≤0.045 ≤0.03 16-18 6-8
202 ≤0.15 ≤1.00 7.5-10
≤0.05 ≤0.03 17-19 4-6
201 ≤0.15 ≤1.00 5.5-7.5 ≤0.05 ≤0.03 16-18 3.5-5.5
3,what kind of stainless steel is not easy to rust?
There are three main factors influencing stainless steel corrosion:
First: the content of alloying elements,
generally speaking, chromium content in 10.5% steel is not easy to rust. The
higher the content of chromium nickel, the better corrosion resistance, such as
304 material nickel content of 8-10%. Chromium content reaches 18-20, such
stainless steel is generally not rusty.
Second, the smelting process of the
production enterprises will also affect the corrosion resistance of stainless
steel. Large stainless steel plants with good smelting technology, advanced
equipment and advanced technology, regardless of the control of alloying
elements, impurity removal. The control of the cooling temperature of billet
can be guaranteed, so the quality of the product is stable and reliable, the
internal quality is good, and it is not easy to rust. On the contrary, some
small steel plants are backward in equipment and technology. In the smelting
process, impurities can not be removed, the production of products will
inevitably rust.
Third: the external environment, the climate
dry and ventilated environment is not easy to rust. And the air humidity,
continuous rainy weather, or the air contains a high degree of acidity and
alkalinity of the environment areas are prone to rust. 304 stainless steel. If
the surrounding environment is too bad, it will rust.
4, Is stainless steel with magnetic good or not? Is 304 stainless steel
with magnetic or not ?
A lot of customers to the market to buy stainless steel itself with a small
magnet, see the goods suck, suck on that is stainless steel. Without a magnetic
rust will not be formed, in fact, this is a wrong understanding. Stainless
steel belt without magnetic structure is determined, the molten steel during
solidification process the solidification temperature of different form of
ferrite, austenite, the "martensitic" different structures
"including stainless steel, ferritic stainless steel, martensite" are
magnetic. And the mechanical properties of austenitic stainless steel, welding
process can be good, but with magnetic from corrosion resistance only "ferrite
stainless steel is stronger than that of austenite stainless steel. The current
market circulation of high manganese containing less nickel containing the
so-called 200 series, 300 series stainless steel is not magnetic, but its
performance and high with 304 big gap, but 304. After stretching, annealing,
polishing, casting and other processes, it will also be microstrip magnetic.
Therefore, it is a misconception and unscientific to judge the quality of
stainless steel with stainless steel strip without magnetism.
5, why does stainless steel also rust?
When the stainless steel surface rust Brown (point) when people are
surprised: "stainless steel will not rust, rust is stainless steel, steel
may be a problem. In fact, this is a one-sided view of the error of the lack of
understanding of stainless steel. Stainless steel under certain conditions will
rust.
Stainless steel has the ability to resist
oxidation of the atmosphere is not a rust, but also with the acid, alkali, salt
tolerance ability of corrosion medium, namely corrosion resistance. But its
corrosion resistance is the size of steel with its own chemical composition,
status, conditions of use and environmental media types and change. 304, in the
dry clean atmosphere, it is absolutely excellent corrosion resistance, but it
will be moved to the beach area, with large amounts of salt fog, they will soon
rust. Therefore, not any kind of stainless steel, can at any time to corrosion,
no rust.
Stainless steel is formed on the surface of a
thin layer of fine solid and stable chromium rich oxide film (protective film),
to prevent the continued infiltration of oxygen atoms, to oxidation, and the
ability to obtain corrosion resistance. But there are some reasons, this film
was constantly destroyed, air or liquid and oxygen atoms will continue to
infiltrate or metal the iron atoms in constant evolution from the loose
formation of iron oxide, the metal surface is being corroded. Many of the
surface damage form, more common in daily life are as follows:
A, the stainless steel surface to deposit
their savings with other metal elements in dust or heterogeneous metal granule
attachments, in the humid air, condensed water and adhesion between the
stainless steel, the two together into a micro battery, causing the
electrochemical reaction, the film has been destroyed, called the
electrochemical corrosion.
B,stainless steel surface adhesion of the
organic juice (such as vegetables, soup phlegm etc.), oxygen in the water under
the circumstances, a long time is the formation of organic acid, organic acid
corrosion on the metal surface.
C, the surface of stainless steel adheres to
acid, alkali, and salt substances (such as the alkali water of the decorated
walls, the lime water spraying), which causes local corrosion.
D, in polluted air (containing a large amount
of sulphide, oxide, hydrogen oxide atmosphere), condensate water, forming
sulfuric acid, nitric acid, acetic acid liquid point, causing chemical
corrosion.
The above conditions can cause damage to the
surface of the stainless steel surface protection film and cause corrosion. So,
in order to ensure permanent light of the metal surface, not to be rusty, we
suggest:
It is necessary to clean and scrub the
surface of the decorative stainless steel regularly, remove the attachments and
eliminate the external factors that cause corrosion.
(2) there is a 201 and 202 stainless steel in
the present market, which is easy to rust in the seashore area, and is suitable
for use without industrial pollution and air corrosion.
(3) the seashore area should use 304
stainless steel, and the 304 material can resist the corrosion of the sea
water.
6, How to deal with the stainless steel rust
spots ?
A) chemical methods:
Using pickling paste or spray assisted
corrosion parts re passivation formation of chromium oxide films make it
restore the corrosion resistance after pickling to remove all contaminants and
acid residues, with water to wash properly is very important. All treated with
polishing equipment RE polishing with polishing wax can be closed. A slight
rust on local the available 1:1 gasoline, oil mixture can rust to clean
dishcloth.
B) mechanical method:
Blast cleaning, cleaning, glass or ceramic
particles shot annihilation, brushing and polishing. By mechanical method could
wipe before removed materials, polishing materials or materials caused by
pollution. All kinds of annihilation pollution especially foreign iron
particles may become the source of corrosion, especially in wet environments.
Therefore, mechanical clean the surface should be regular cleaning best in dry
conditions. The use of mechanical method can only clean the surface, can not
change the material corrosion resistance. So in the mechanical cleaning after
re polishing with polishing equipment, closed with polishing wax.
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